The overall objectives of this program are to identify and isolate a membrane structural unit (carrier) which is responsible for the so-called "carrier-mediated" transport, common to many biologically important solute transport across natural membranes including "pump". An eventual goal of the project is to reconstitute in vitro from such an isolate the carrier function, and study the mechanisms of the carrier operation at a molecular level. More specific objectives set for the current research year was to identify the carrier components in the human erythrocyte membranes which mediate the movements of glucose and other sugars. Particularly studied was the effect of 1-fluoro-2,4-dinitrobenzene (FDNB) on the carrier-mediated glucose flux across the carrier-intact, practically hemoglobin-free human erythrocyte ghost membrane. The compound inhibits the carrier function irreversibly. Furthermore, the inactivation is modified drastically by the carrier-substrate, D-glucose, in many respects. These include the rate of inactivation, the order of the reaction with respect to FDNB, the temperature-dependency, and the pH-dependency. Bulk membrane dinitrophenylation, on the other hand, is not affected by the sugar to any appreciable extent. A number of other well known SH-reagents reveals similar but not exactly identical effects as FDNB. Another aspect of the studies was to differentially tag the carrier components separately from other membrane components by FDNB, based on the unique behavior of this compound outlined above. A group of peptides with estimated molecular weight ranging 150-200 x 10 to the 3rd power is identified on SDS-gel electrophoresis, which react much more readily with FDNB in the presence of D-glucose. Beside the studies with FDNB, an attempt was also made where the differential tagging of the carrier is approached by derivatives of D-glucose having a protein-reactive group. Synthesis of such reagents (derivatives) is currently actively looked upon in this laboratory.